I don't think you have to run a 180 but I beleive the fans are set to come on at lower temps with the PCM and the stock 195 will probably have them on all the time. It's only $10 and 2 bolts I say change it, the car will still warm up fine in the winter if that is the issue.
Wait a minute, I just saw you are in NM, why don't you want to change to a 180?
I can vouch from experience that a 180 thermostat has absolutely no effect on gas mileage whatsoever. Driving style, intake, and exhaust are the biggest factors aside from removing all the stuff GM stuffed in there to improve it. (vapor canister, EGR, etc...)
If you plan on modding the car at all, 180 T-stat is highly recommended (if not considered mandatory) as one of the very first things done to the car. Heat is your enemy. If you decide not to install a 180, be sure to tell the PCM maker this so they can set your fan speeds appropriately.
BTW, I did not noticed any MPG change with a 180. In fact most of the first mods like rockers and exhaust mods will increase your MPG if you can keep your foot off of the powerbar
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